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ADS41b29 CMOS Mode

ibrahim topal
Prodigy 90 points

Hi,

I'm trying to set the ADC to CMOS mode. My register settings are:

        0x03, 0x03,
        0x25, 0x50,
        0x3D, 0x80,
        0x3F, 0x1F,
        0x40, 0xFF,
        0x41, 0xC0,
        0x42, 0x08,
        0x43, 0x00,
        0x4A, 0x01

My CLK is 166.66MHz. I cannot see any CLKOUT signal on the pins 4 or 5.

My questions are:

1) Are the registers correct? Do I have to set any other register than 0x41 for CMOS? The DFS pin should be irrelevant for this setting, right?

2) Which pin is the CLKOUT in CMOS mode?

  • 0
    TI__Genius 17290 points

    Hi Ibrahim,

    You must hold RESET low to use the serial interface. If RESET is held high then the output format will be based on the DFS pin. You must also either pulse the RESET pin or use the software RESET (Reg 0x00) to reset the registers. You can then program the registers. Your register settings look fine. CLKOUT should be on pin 5 in CMOS mode.

    You must apply a clock to the ADC in order to get the clock out. You seem to indicate that this was done.

    Another thing to look at is to make sure your SPI interface is working correctly. Try to probe the SPI signals and verify that the data is what you expect.

    Regards,
    Matt Guibord

  • 0 in reply to Matt Guibord
    Prodigy 90 points

    Hi Matt,

    Thank you for your answer but I have already configured the registers as you described. My SPI communication is also OK, I can see the test signals and custom patterns. I supply the clock as well but no DCO is seen on pin5. Do you have any other idea?


    Regards,

    Ibrahim

  • 0 in reply to ibrahim topal
    TI__Genius 17290 points

    Hi Ibrahim,

    Have you been able to observe an LVDS clock?

    To rule out SPI settings, lets try to configure the ADC using the parallel mode. Simply toggle the RESET pin to reset the part. The DFS pin will then control the output format based on table 4 in the datasheet. You should be able to observe a clock output in either LVDS or CMOS format, depending on how DFS is wired. If no clock is seen, then this seems to point toward either a circuit issue or a manufacturing defect.

    Regards,
    Matt Guibord

  • 0 in reply to Matt Guibord
    Prodigy 90 points

    Hi Matt,

    I was able to see the LVDS clock and data. The problem is with the CMOS, I have tried Register configuration and and DFS pin with no success. No CLKOUT on pin 5 or 4 although everything is OK with LVDS.

    Regards,

    Ibrahim

  • 0 in reply to ibrahim topal
    TI__Genius 17290 points

    Hi Ibrahim,

    I just setup the EVM. After resetting the part I see an LVDS clock on pins 4 and 5. I then write 0xC0 to address 0x41. I'm now able to see a CMOS clock on pin 5 of the ADC. Pin 4 is held at ground. If you're using the EVM can you please try this simple test?

    The jumpers are setup as such:
    JP9 = 2-3
    JP12 = 2-3
    JP11 = 2-3

    In the ADS41xx GUI, I am simply pressing the "RESET" button and then the "Output Interface" button.

    Regards,
    Matt Guibord